<style>
    .left {
        width: 200px;
        height: 600px;
        background: red;
        float: left;
        display: table;
        text-align: center;
        line-height: 600px;
        color: #fff;
    }

    .right {
        margin-left: 210px;
        height: 600px;
        background: yellow;
        text-align: center;
        line-height: 600px;
    }
</style>
<div>
    <div class="left">定宽</div>
    <div class="right">自适应</div>
</div>